How can you tell if you have a collapsed lung?

Doctor's exam, Xray. Symptoms of pneumothorax (collapsed lung) include sharp chest pains (especially with breathing), a dry cough, and shortness of breath. If the leaked air is compressing the lungs and heart, it is a tension pneumothorax (life-threatening!) and symptoms include a very anxious looking person with trouble breathing or talking, swollen veins in the neck, & bluish skin color (cyanosis). Confirm by x-ray.

X-ray. No way to know chest pain short of breath are symptoms.